#include <iostream>
using namespace std ;

//根据给出思路：f(n) = f(n-1) + f(n-2) (n>2)

int main(){
	int a=1,b=2,n ;//a = f(1)，b = f(2)
	
	for (int i=1; i<=8; i++){
		n = a + b ;
		a = b ;
		b = n ;
	}
	
	cout << n ;//求第十项
	
	return 0 ;
}
